A Hole-Burning Study of the Zero-Field Splitting of the Triplet Ground and Excited States of 2,2-Dinaphthylcarbene in n-Heptane and n-Hexane at 1.7 K

Spectral holes were burned within the inhomogeneous 0,0 fluorescence excitation lines of the T0 → T1 transition of 2,2-dinaphthylcarbene (2,2-DNC) in n-heptane at 1.7 K. The spectrum of holes, attributed to the Z/cis conformer of 2,2-DNC, was interpreted with a model taking into account the zero-field splitting (zfs) of both triplet states contributing to the transition, enforced C 2 v symmetry, and the dominance of internal conversion in the relaxation of the excited T1 state. Under enforced high symmetry, the number of possible electronic transitions between different spin sublevels of the ground T0 and excited T1 states is reduced and the analysis of spectral position of holes can only provide the differences between the zfs parameters: D 0 − D 1 = 0.558 ± 0.001 cm-1 and E 0 − E 1 = 0.0183 ± 0.001 cm-1.